package Practice;
import java.util.Scanner;
public class FindFibo {
    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
        int n=scan.nextInt();
        int c=0;
        int a=1,b=1;
        while(n>2){
            c=a+b;
            a=b;
            b=c;
            n--;
        }
        System.out.println(c);
    }
    //1 1 2 3 5 8 13 21 34 55
}
